1. Field of the Invention
The present invention relates, most generally, to apparatuses for storing substrates, and more particularly to front opening unified pods (FOUPs).
2. Description of the Related Art
With advances in electronic products, semiconductor technology has been applied widely in manufacturing memory devices, central processing units (CPUs), liquid crystal displays (LCDs), light emitting diodes (LEDs), laser diodes and other devices or chip sets. In order to achieve high-integration and high-speed requirements, dimensions of semiconductor integrated circuits have been reduced and various materials, such as copper and ultra low-k dielectrics, have been proposed along with techniques for overcoming manufacturing obstacles associated with these materials and requirements.
FIG. 1A is a schematic drawing showing a traditional via hole structure. A copper layer 110 is formed over a substrate 100. An ultra low-k dielectric layer 120 is formed over the copper layer 110. A via hole 130 is formed within the ultra low-k dielectric layer 120 to expose the top surface of the copper layer 110. If the copper layer 110 is exposed to air, the top surface of the copper layer 110 reacts with oxygen in air, forming a copper oxide layer 140 due to oxidation. The copper oxide layer 140 can adversely affect the electrical connection between the top surface of the copper layer 110 and a conductive via plug filled into the via hole 130. In addition, the ultra low-k dielectric layer 120 absorbs moisture when exposed to air. Accordingly, great care should be taken to avoid exposure to air during critical process steps, such as via opening, the formation of copper seed layers in the via opening, chemical mechanical polishing (CMP) of the copper and formation of the ultra low-k dielectric material.
Traditionally, after a critical process step, the substrate 100 is removed from the process chamber that performs the critical process step and temporarily stored in a FOUP 150 shown in FIG. 1B until subsequent processing. The substrate 100 is stored in the FOUP 150 to reduce the exposure of the copper layer 110 to atmosphere.
FIG. 1B is a schematic cross-sectional view of a prior art FOUP. The FOUP 150 protects wafers stored therein from being contaminated by particles within the environment having airborne molecular contamination (AMC) around the FOUP 150. AMCs in a fab generally come from the process chemicals, outside air, cleanroom materials and process tools. Due to airflow designs in the fab, one area may contaminate adjoining one due to recirculation. Fab exhaust, adequately scrubbed to meet regulatory requirements at parts per million (ppm) levels, can be pulled back into the fab on a calm day by the air intakes, which can cause AMC problems in the fab. Cleanroom construction materials and process equipment can also be a significant source of contamination. The FOUP 150 includes an enclosure 160 and a door 170. The enclosure 160 includes a frame 165. The enclosure 160 also includes outlet check valve 173 and inlet check valve 175.
During removing the door 170 or open the enclosure 160, AMC diffuses into the enclosure 160. After the door 170 is transferred to close the enclosure 160, AMC remains in the enclosure 160. In order to remove AMC in the enclosure 160, the inlet check valve 175 is disposed at the bottom of the enclosure 160 through which nitrogen is provided into the enclosure 160 to carry away AMC from the enclosure 160. Nitrogen provided within the enclosure 160 may push the door 170 away from the enclosure 160. The outlet check valve 173 is disposed at the bottom of the enclosure 160 through which AMC within the enclosure 160 can be removed partially removed.
When the door 170 is configured to close the enclosure 160, the door 170 is transferred and contacts a gasket 180 so as to close the enclosure 160 and prevent particles flowing into the enclosure 160. When the enclosure 160 is removed, the door 170 is unlocked and transferred directly away from the enclosure 160.
Based on the foregoing, an improved apparatus for storing substrates are desired.